Production of cycloalkanone oximes by the reduction of cyclic nitro paraffins



United States Patent PRODUCTION OF CYCLOALKANONE OXIMES BY 511%REDUCTION OF CYCLIC NITRO PARAF- Johannes H. Ottenheym, Sittard,Netherlands, assignor to De Directie van de Staatsmijnen in Limburg,handelend voor en namens dc Staat der Nederlanden, Heerlen, NetherlandsNo Drawing. Application March 26, 1951, Serial No. 217,691

Claims priority, application Netherlands March 31, 1950 10 Claims. (Cl.260--566) This invention relates to the production of cycloalkanoneoximes by the reduction of cyclic nitro paraffins.

FIELD OF INVENTION Many processes are known for the reduction of nitrocompounds in which amines are obtained. If it is desired to manufactureoximes from the nitro compounds, the reduction process must be carriedout in such a maunor that oxime is formed as an intermediate reductionproduct which, under the given. reaction conditions, cannot be reducedfurther to an amine. The reactions involved are represented by thefollowing formula:

wherein R1 is an organic radical and R2 is an organic radical orhydrogen.

This type of reaction can be partly attained by reducing the sodiumcompound of the nitro parafiin with tin or zinc in an acid medium,preferably by means of hydrochloric acid. However, when such a reductionis carried out, only low yields of oxime, about 40 to 50% by weightbased on the nitro compound, are obtained, amines and ketones beingformed as by-products.

Oximes can also be manufactured by reducing sodium salts of nitroparaffins with hydroxylamine compounds, but in this case, the reductionmust be carried out at a low temperature, below 5 C., so that intensivecooling is necessary, and the reducing agent is expensive.

OBJECTS (2) The provision of new reducing reagents for use in suchreactions.

(3) The provision of such reactions which may be carried out at normaltemperatures and pressures, thus eliminating need for complex cooling orother complicated apparatus.

(4) The provision of new methods for making cycloalkanone oximes inwhich the oximes may be produced in relatively high yields.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the 2,799,179 PatentedMay 24, 1955 spirit and scope of the invention will become apparent tothose skilled in the art from this detailed description.

GENERAL DESCRIPTION These objects are accomplished according to thepresent invention through the reduction of nitrocycloalkanones using asolution of an inorganic sulfide as the reducing agent. Preferably, thenitrocycloalkane, such as nitrocyclohexane, is dissolved in a solvent,such as a lower aliphatic alcohol, to which a solution of inorganicsulfide is added or formed in situ, by the introduction of materials toform an inorganic sulfide, e. g., by the introduction of ammonia andhydrogen sulfide.

The success of this invention is due, to a large extent, to thesurprising discovery that reduction of nitrocycloalkanes with solublesulfides leads to the formation of high yields of oximes. This isunique, because the formation of amines, instead of oximes, is to beexpected, since it is established practice to employ soluble sulfides asreducing agents in the manufacture of amines from the correspondingaromatic nitro compounds,

The manner in which these new discoveries can be utilized and thedetails of operation, according to the present invention, can be morefully comprehended by reference to the following illustrative examplesof actual operations, in accordance with the invention.

Example I At a temperature of about 100 C. and in the absence of air, 2gram moles of sodium hydrosultide are added with moderate stirring to asolution of 1 gram mole of nitrocyclohexane in 2 litres of butanol.After a reaction period of 20 minutes, 55% by weight of thenitrocyclohexane is reduced. The yield of recovered oxime amounts tobased on converted nitrocyclohexaue.

Example I] In an analogous manner as described in Example I, thereduction is carried out with ammonium polysulfide at a temperature of70 C., while ethanol is used as a solvent. The yield of oximecorresponds to 95 of the converted initial material.

Example III Into a solution of nitrocyclohexane in ethanol containing0.1 gram mole of nitro compound per litre, equimolecular amounts ofammonia and hydrogen sulfide are introduced at room temperature. After areaction period of about 1 hour, 95% of the nitrocyclchexane is reducedto the corresponding oxime.

DETAILED DESCRIPTION The new procedures are generally applicable tonitrocycloalkanes (also called cyclo nitro paraflins). The examplesillustrate the use of nitrocyclohexane for this purpose, but otherusable materials include:

Nitrocyclopropane Nitro-2,5-dimethyl cyclohexane Nitro-Z-methylcyclohexane Nitro-4-isopropyl cyclohexane NitrocyclopentaneNitro-Z-methyl cyclopentane The reducing agents employed in the processare soluble, inorganic sulfides, such as the neutral or acid sulfides ofthe alkali metals, the alkaline earth metals and ammonia. Likewise, thepolysulfides of these metals or of ammonia may be used.

The sulfide employed as a reducing agent may be added in a dissolvedcondition to the nitro compound to be reduced. It is also possible todissolve the nitro compound in the solvent and to add the sulfide to theresulting solution. Furthermore, the nitro compound may be emulsified inthe sulfide solution.

According to the preferred embodiment, equimolecular amounts of hydrogensulfide and ammonia are passed into an alcoholic solution of the nitrocompound in which case the sulfide reducing agent is formed in thereaction mixture. It is also pos sible to introduce H28 into a solutionof nitrocyclohexane and alkali hydroxide or alkaline earth hydroxide.

The sulfides are employed as a solution preferably in an organicsolvent, especially, a lower aliphatic alcohol, e. g., ethyl alcohol,propyl alcohol, or butyl alcohol, but other solvents, such as water, maybe used. The proportions of solvent to the reducing agent or, in turn,to the nitrocycloalkane are not critical and ratios of 1 to parts ofsolvent for each part of sulfide, and 1 to parts of solvent for eachpart by Weight of nitrocycloalkane are representative of preferredratios.

Preferably, the reaction is carried out at ordinary pressure, since thiseliminates the need for complicated apparatus and because the reactionproceeds with very favorable results at these pressures. the reactionout at a temperature above the boiling point of the solvent, elevatedpressure may be used or suitable condensing apparatus may be employed.it is desirable to carry out the reduction under non-oxidizingconditions in order to avoid oxidation of sulfides, so that a slightover-pressure may conveniently be maintained in the apparatus by meansof nitrogen.

The reduction can proceed satisfactorily at room temperature, i. e.,about 15 C., but if more rapid reaction is required, this can beobtained by operating at higher temperatures, for example, 50 to 150 C.,making the preferred temperature range between 15 and 150 C. At thesetemperatures, the reaction time usually is between 10 and 120 minutes,especially 10 to 60 minutes.

The proportions of sulfide to nitrocycloalkane are not critical and maybe varied, although for most desirable results stoichiometricproportions of sulfide or a slight excess thereof, for example, between2 and 3 moles of sulfide for each mole of nitrocycloalkane, areemployed.

Although it is possible for some purposes to use the resulting solutionscontaining the oxime products with out separation of the oximetherefrom, it is generally desirable or necessary to recover the oximcfrom the reaction liquors. Any known method can be employed for thispurpose, such as extraction of the solution with a preferential solventfor the oxime, precipitation of the oxime by addition of incompatiblematerials, or by evaporation of these solvents subsequent to removal ofundesired nonvolatile components from the reaction liquors.

CONCLUSION A new method for making oximes from the correspondingnitrocycloalkanes in high yields and in an easily conducted manner hasbeen described. The reaction has wide application and may be employed toproduce a large variety or" oximes of cycloalkanes.

I claim:

1. in a process for the production of cycloalkanone oximes, the stepwhich comprises reducing a nitrocycloalkane with a solution of aninorganic salt of hydrogcn sulfide in an inert solvent.

2. In a process for the production of cycloalkanone oximcs, the stepwhich comprises reducing a. nitrocyclo- If it is desired to carry alkanewith a solution of an inorganic salt of hydrogen sulfide in an inertsaturated, lower aliphatic alcohol.

3. In a process for the production of cycloalkanone oximes, the stepwhich comprises reducing a nitrocycloalkane with a water solution of aninorganic salt of by drogcn sulfide.

4. A process as claimed in claim 1, wherein said reaction is conductedat a temperature between 15 and 150 C.

5. A process for the production of a cycloalkanone oxime which comprisesproviding a solution of a nitro cycloalkane in an inert saturated, loweraliphatic alcohol, introducing ammonia and hydrogen sulfide into saidsolution and continuing said gas introduction until saidnitrocycloalkane is substantially completely reduced to a correspondingoxime.

6. A process for the production of a cycloalkanone oxime which comprisesproviding a solution of a nitrocycioalkane in an inert saturated, loweraliphatic alcohol, introducing an inorganic sulfide from the groupconsisting of alkali metal, alkaline earth metal and ammonium sulfidestherein, allowing the admixed material to react at 15 to 150 C. forabout it) to 120 minutes and recovering a cycloalkanone oxime from thereaction mixture.

7. A process as claimed in claim 6, wherein said inorganic sulfide isintroduced into said solution by adding hydrogen sulfide and a member ofthe group consisting of the corresponding alkali metal hydroxide,alkaline earth metal hydroxide and ammonia to the solution.

8. A process for the production of cyclohexanone oxime which comprisesforming a solution of nitrocyclohexane in an inert saturated lower:aliphatic alcohol, heating the solution to about to 0, adding about 2moles of an inorganic salt or" hydrogen sulfide for each mole ofnitrocyclohexane to said solution, allowing the materials to react forabout 10 to 60 minutes, and recovering cyclohexanone oxime from thereaction mixture.

9. A process as claimed in claim 8, wherein said alcohol is butanol and.said sulfide is sodium hydrosulfide.

10. A process as claimed in claim 8, wherein said alcohol is ethanol andsaid sulfide is ammonium polysulfide.

References Cited in the file of this patent UNITED STATES PATENTS Fieserand Fieser, Organic Chemistry, 2nd ed., 1950, D. C. Heath and (10.,Boston, Mass, pp 617 and 634. Hartman et al., Organic Syntheses, vol.25, 1945, pp. 5-7.

1. IN A PROCESS FOR THE PRODUCTION OF CYCLOALKANONE OXIMES, THE STEPWHICH COMPRISES REDUCING A NITROCYCLOALKANE WITH A SOLUTION OF ANINORGANIC SALT OF HYDROGEN SULFIDE IN AN INERT SOLVENT.